British police said Wednesday that two people found unconscious over the weekend were poisoned by Novichok, the same nerve agent used against ex-Russian spy Sergei Skripal and his daughter. The two new victims, a man and a woman, were found Saturday in Amesbury, which is located about eight miles away from Salisbury, where Skripal and his daughter were stricken in March.

The two latest victims were still in critical condition on Wednesday morning.

Police said it is unclear if this incident is linked to the earlier poisoning of Sergei and Yulia Skripal, or if the batch was the same as the one that poisoned them on March 4.

Police say no on else has presented with the same symptoms, according to BBC News. Medical officials said Wednesday people who had been in the area where the couple had been should take precautions and wash their clothes.

Counterterrorism police detective Neil Basu said it is unclear if the couple were targeted or if the poisoning was accidental. There was “nothing in their background” to suggest the pair were targeted, police said.

Counterterrorism officials are now leading the investigation, according to BBC News.